Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts destinations client‑side, stores ciphertext on a blockchain, and decrypts in the browser, eliminating tracking and central data breaches.

Problem

Traditional URL shorteners log user data, track browsing patterns, and sell data, creating privacy risks and a single point of failure.

Outcome

The system provides a URL shortener that never sees the destination URL, eliminates tracking, and stores data on an immutable blockchain, enhancing privacy and resilience.

Workflow

• Generate a random IV and AES‑GCM key in the browser.
• Encrypt the destination URL with Web Crypto API.
• Send the ciphertext to a Cloudflare Worker.
• Worker writes the ciphertext to the Cronos blockchain via a transaction.
• User accesses the short link, Worker fetches ciphertext from blockchain.
• Browser decrypts ciphertext locally and redirects to the original URL.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source